In the production process of electronic devices, a variety of treatments have been performed on the electronic device substrate (substrate to be treated). In the case of, for example, a semiconductor as the electronic device, a semiconductor wafer (wafer) is loaded; after that, a film-forming step of forming an insulating film or a metal film, a photolithography step of forming a photoresist pattern, an etching step of processing the film using the photoresist pattern, an impurity-adding step of forming a conductive layer on the semiconductor wafer (also called doping or diffusion process), a CMP step of polishing the uneven surface of the film to flatten the surface (chemical mechanical planarization), and the like are performed, followed by semiconductor wafer electrical characteristics inspection for inspecting the finish of the pattern or the electrical characteristics (these steps may be collectively referred to as the front-end process). Subsequently, the back-end process of forming semiconductor chips follows. This front-end process is also performed not only when the electronic device is a semi conductor, but also when other electronic devices (e.g., light-emitting diodes (LED), solar batteries, liquid crystal displays, and organic EL (Electro-Luminescence) display) are produced.
The front-end process includes, in addition to the steps described above, a washing step using plasma, ozone, ultraviolet rays, and the like, and a step of removing a photoresist pattern using plasma, radical-containing gas, and the like (also called ashing or ash removal). The film-forming step also includes CVD for forming a film by chemically reacting a reactive gas on the wafer surface, and sputtering for forming a metal film. The etching step includes, for example, dry etching performed by chemical reaction in plasma, and etching by ion beams. The “plasma” refers to the state in which gas is dissociated, and ions, radicals, and electrons are present in the plasma.
In the production process of electronic devices, the various treatments described above must be properly performed to secure the performance, reliability, and the like of electronic devices. Thus, in the plasma treatment represented by a film-forming step, an etching step, an ashing step, an impurity-adding step, a washing step, etc., a completion check and the like is performed to confirm the completion of the plasma treatment, for example, by emission analysis of plasma with a spectrometer, or by using a plasma treatment detection indicator comprising a color-changing layer that changes color in a plasma treatment atmosphere.
As an example of the plasma treatment detection indicator, Patent Literature 1 discloses an ink composition for detecting a plasma treatment comprising 1) at least one of anthraquinone colorants, azo colorants, or phthalocyanine colorants; and 2) at least one of binder resins, cationic surfactants, or extenders, wherein a plasma-generating gas used in the plasma treatment contains at least one of oxygen or nitrogen. Patent Literature 1 also discloses a plasma treatment detection indicator comprising a color-changing layer that comprises the ink composition formed on a base material.
Patent Literature 2 discloses an ink composition for detecting inert gas plasma treatment, comprising (1) at least one of anthraquinone colorants, azo colorants, and methine colorants; and (2) at least one of binder resins, cationic surfactants and extenders, the inert gas containing at least one selected from the group consisting of helium, neon, argon, krypton, and xenon. Patent Literature 2 also discloses a plasma treatment detection indicator in which a color-changing layer comprising the ink composition is formed on a base material.
However, the check method, using emission analysis or a traditional plasma treatment detection indicator may be insufficient in performance as .an indicator for use in an electronic device production equipment. Specifically, because of the limitation to the measurement and analysis performed through the window provided to the electronic device production equipment, it tends to be difficult to perform efficient measurement or analysis with the check method using emission analysis when the inside of the electronic device production equipment cannot be thoroughly seen. Although the use of a traditional plasma treatment detection indicator is a convenient and excellent means for confirming the completion of plasma treatment through the color change of the color-changing layer, the organic colorants as a color-changing material may possibly lead to decreased cleanliness of the electronic device production equipment or contamination of electronic devices due to gasification of the organic colorants or scattering of the fine debris of the organic colorants caused by plasma treatment. The gasification of color-changing changing material may adversely affect the vacuum performance of the electronic device production equipment. In addition, because of the insufficient heat resistance of the traditional color-changing layer comprising organic colorants as a color-changing material, it is difficult to use it as an indicator when the electronic device production equipment has a high temperature.
Therefore, there has been a demand for the development of a plasma treatment detection indicator comprising a color-changing layer that changes color by plasma treatment, exhibiting excellent heat resistance with the gasification of the color-changing material or the scattering of the fine debris of the color-changing material caused by plasma treatment being suppressed to the extent that electronic device properties are not affected.